Using projected monthly mean sea surface tem-perature (SST) in the 21st century obtained by multiple climate models and SST-based indices for the poleward range expansions of three types of coral habitats, we quantitatively evaluated the effects of SST warming on potential northern limit of coral habitats in seas close to Japan and their uncertainty in the global warming pro-jections. The uncertainty in the timing of temperate coral community formation due to global warming was no less than 30 years, with a modulation of ±10 years due to decadal climate variability. Tropical-subtropical and tem-perate coral communities and coral occurrence in seas close to Japan were predicted to shift poleward by a few hundred kilometers by the end of the 21st century. The average estimated speeds of the shifts were 1, 2, and 4 km/year for the tropical-subtropical coral community, temper-ate coral community, and coral occurrence, respectively. The simulated speeds were relatively slower than those previously observed (up to 14 km/year; Yamano et al. 2011), indicating that there are time lags between the new recruitment of coral colonies and the establishment of coral communities. Hence, monitoring of coral dynamics in response to SST warming is required. Collaboration between monitoring and modeling would enhance the reliability of future projections of changes in coral ha-bitats. Such projections are important for conserving marine biodiversity and developing plans for human societies to adapt to global warming.
Quantification of zooxanthellae densities in tissues of reef-building corals aids in the assessment of the extent and severity of coral bleaching. Various meth-ods are available to quantify zooxanthellae densities; how-ever, a direct comparison of these techniques has yet to been done. Here, we compare estimates of zooxanthellae densities obtained using conventional airbrushing coupled with post-tissue-blasting surface area determination, ver-sus a technique whereby zooxanthellae densities are quantified from a known area (0.25 cm2) of tissue after corals have been fixed and decalcified. Estimates of zoo-xanthellae densities obtained were correlated across re-plicate colonies (R2=0.40, n=81), and both techniques revealed similar patterns of variation among locations. The main benefit of the decalcification technique was reduced processing time, because the technique eliminates the time-consuming process of tissue blasting and re-trospective estimates of surface area. We estimate that decalcification halves the processing time per sample, and produces a more accurate estimate of zooxanthellae density.
The cyanobacteriosponge Terpios hoshinota encrusts living coral and other benthos, and occasionally undergoes massive outbreaks, resulting in large amounts of damage to coral reef ecosystems. At the same time, this species is theorized to be expanding its range in the northwestern Pacific. Despite this, the current distribution of this species in Japan is unknown, with no research having been conducted since an initial assessment in 1984-1985. To address this information deficiency, a survey of the Ryukyu Archipelago from Amami Oshima Island south to the Yaeyama Islands was conducted to assess the distribution of T. hoshinota over the period of 2009 to 2011. Field images have been posted as an online image archive for researchers to utilize in future research. Our findings show that the presence of T. hoshinota is not uncommon in this region, with at least 23 of 64 (=36%) sites with this species. This is a considerable increase from levels reported in 1984-1985 (11 of 182 sites, =6%), and suggests this species is now a permanent feature in the coral reef ecosystems of this region. However, large outbreaks were at approximately the same levels as reported in 1984-1985. Most T. hoshinota were found in shallow (<5 m) depths, and abundance does not appear to be greatly influenced by seasons. It may be that general degradation of reefs in these decades has contributed to the spread of this species. Long-term monitoring and additional research are needed to assess the threat T. hoshinota poses to the coral reefs of southern Japan.